#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS

#include <algorithm>
#include <cmath>
#include <cstdio>
#include <ctime>
#include <deque>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define all(x) (x).begin(),(x).end()
typedef long long ll;

typedef vector<int> VI;
typedef vector<string> VS;
typedef vector<VI> VVI;

typedef pair<int,int> PII;
typedef vector<PII> VPII;
#define X first
#define Y second
#define mp make_pair

#define two(x) (1<<(x))
#define twoll(x) ((long long)1<<(x))
#define contain(s,x) (((s)&two(x))!=0)
#define containll(s,x) (((s)&twoll(x))!=0)

#define db(a) cout << #a << "=" << a << " "
#define dbn cout << endl
#define sqr(x) (x)*(x)

string STR(int n) { char tmp[20]; sprintf(tmp,"%d",n); return tmp; }
int INT(string s) { return atoi(s.c_str()); }
template <class Ty, class Tx> Ty to(const Tx &x) { Ty y; stringstream ss; ss<<x; ss>>y; return y; }

const int INF = 1000000007;
const double EPS = 1e-10;

char buf[1<<20];
int TC;

int N,M;

int main() {
#define SUBMIT 0
#if !SUBMIT
	freopen("DATA.in", "rt", stdin);
	freopen("DATA.ou", "wt", stdout);
#endif

	gets(buf); TC = atoi(buf);
	
	while (TC--) {
		scanf("%d",&N);
		VPII vp;
		for (int i = 0; i < N; ++i) {
			int a,b;
			scanf("%d%d",&a,&b);
			vp.push_back(mp(a,b));
		}
		scanf("%d",&M);
		sort(all(vp));
		
		int res = 0;
		int val = 0;
		while (true) {
			int sum = 0;
			bool ok = 1;
			for (int i = 0; i < vp.size(); ++i) {
				int a = vp[i].X;
				int b = vp[i].Y;
				if (val-b < 0 || (val-b)%a != 0) {
					ok = 0;
					break;
				}
				sum += (val-b)/a;
			}
			if (ok)
				if (M == sum) {
					res = val;
					break;
				}
				else if (sum > M)
					break;
			int a = vp.back().X;
			int b = vp.back().Y;
			if (!(val-b < 0 || (val-b)%a != 0) && (val-b)/a >= M)
				break;
			++val;
		}
		printf("%d\n",res);
	}

	return 0;
}





